Treatment of a cross-linking agent-impregnated cellulosic fabric with a gaseous acid catalyst

ABSTRACT

A fabric comprising cellulose or a blend thereof which may or may not be premercerized or prealkylated is impregnated with an aldehyde or an aldehyde liberating compound and thereafter exposed to acidic vapors to catalyze the reaction. Softening agents, bluing agents, formaldehyde catchers, optical brighteners, etc., may be included in the impregnating bath.

0 United States Patent 1151 3,663,974 Watanabe et al. 451 Ma 23, 1972 TREATMENT OF A CROSS-LINKING References Cited AGENT-INIPREGNATED CELLULOSIC UNITED STATES PATENTS FABRIC WITH A GASEOUS ACID 2,235,141 3/1941 Dreybus et a1 ..117/62.2 CATALYST 2,311,080 2/1943 ...s/116.4 [72] lnventors: Kumao Watanabe; Tooru Ma'tuunoto; 244l859 5/1948 16A Tami Nak a" fM 2,512,195 6/1950 8/1l5.6 Japan 3,046,079 7/1962 8/1 16.4 73 Assignee: Toyo Spinning C0., Ltd., Kita-ku, Osaka, 3,154,373 10/1964 8/116-4 Japan 3,175,874 3/1965 ...8/l15.6

3,189,404 6/1965 Takizaki et al. ..8/1l6. [22] Filed: Mar. 6, 1968 OTHER PUBLICATIONS [21] Appl. No.1 711,136

Guthrie, Textile Research Journal, vol. 29, pp. 834- 835 Related U.S. Application Data 1959) [63] Continuation of Ser. No, 238,294, Nov. 16, 1962, Primary Examiner Gerge F Lesmes abandoned- Assistant Examiner-J. Cannon Att0mey--Wcnder0th, Lind & Ponack [30] Foreign Application Priority Data Nov. 28, 1961 Japan ..36/43158 [57] ABSTRACT A fabric comprising cellulose or a blend thereof which may or I 52] U.S. Cl ..8/1 16.4, 8/ 1 15.6, 8/1 15.7, may not be premercerized or prealkylated is impregnated with 8/ 1 16.2, 8/1 16.3, 8/120, 8/ 125, 8/129 an aldehyde or an aldehyde liberating compound and 51 Int. 01 ..D06m 1/16, D06m 13 14 thereafter exposed to acidic vapors to catalyze the reaction- [58] Field of Search ..8/l16.4 sfiening agems, bluing agents, maidehyde catchers,

cal brighteners, etc., may be included in the impregnating bath.

8 Claims, No Drawings TREATMENT OF A CROSS-LING AGENT- IMPREGNATED CELLULOSllC FABRIC WITH A GASEOIUS ACID CATALYST This application is a continuation of application Ser. No. 238,294, filed Nov. 16, 1962 and now abandoned.

The present invention relates to the treatment of fabrics containing cellulosic fibers (natural or regenerated) to reduce their tendencies toward creasing and wrinkling both in wet and dry state or to enhance the dry and wet resilience or crease resistance of the fabrics without adversely affecting desirable properties and characteristics, particularly the wet and dry strength, of the fabrics.

It is well known that when a cellulosic fabric is impregnated with formaldehyde together with a strong acid and subjected a cross-linking reaction, the tendency of the fabric to wet creasing may be reduced. This treatment, however, is not satisfactory to produce real wash and wear" fabric because it fails to provide the fabric with a sufficient dry crease-resistance. Still further drawback of the conventional formaldehyde-strong acid treatment wherein formaldehyde and the strong acid are simultaneously applied in liquid state to a fabric is that the satisfactory wet crease-resistance is obtained only with a considerable sacrifice of the mechanical strength such as tearing strength, tensile strength, etc. of the fabric.

To improve the dry crease-resistance it has been proposed to treat a cellulosic fabric with a resinous substance (e.g. aminoplast resin) after the fabric has been subjected to the conventional formaldehyde-strong acid treatment. Apparently such an additional treatment would be time-consuming and require additional cost. Furthermore, the desired mechanical strength of the fabric is further reduced by such additional treatment. A further drawback of the conventional resin treatment is in the fact that the resin is removed or washed away from the fabric gradually by repeating the laundry so that it is impossible for the fabric to retain the desired wash and wear performance for a prolonged period of time.

it is an object of the invention to provide a single method of treating a cellulosic fabric to enhance both the wet and dry resilience of crease resistance and flat drying properties thereof.

it is another object of this invention to provide a method for treating a cellulosic fabric to impart thereto a highly desirable balance of properties and characteristics including a high degree of both wet and dry resilience with a minimization of strength loss.

it is still another object of this invention to provide a method for treating a cellulosic fabric to impart thereto desirable properties or wet and dry resilience which is retained even after repeated laundering.

An additional object of this invention is to provide a method of producing a wash and wear fabric having soft and smooth hand.

Briefly, these and other objects of this invention are accomplished by impregnating a cellulosic fabric with an aqueous liquid containing an aldehyde or a substance which is capable of liberating an aldehyde (in the absence of a strong acid catalyst in contrast to the conventional method) and then contacting the fabric with gaseous hydrochloric, sulfur trioxide or sulfur dioxide while maintaining the moisture content of the fabric below 20 percent (preferably between 6 and percent) by weight.

The process of this invention is applicable to fabrics containing cellulosic fibers (either natural or artificial) alone or as mixtures of two or more in various proportions or as mixtures with other fibers. As natural cellulosic fibers, cotton, linen, hemp, etc. may be exemplified, and among artificial cellulosic fibers are, for example, viscose rayon, cupra ammonium rayon and other regenerated cellulosic fibers. Other fibers which may be used with one or more of the above mentioned cellulosic fibers are, for example, cellulose acetate, polyamides, polyesters, polyacrylonitriles, polyolefines, polyvinyl chlorides, polyvinylidine chlorides, polyvinyl alcohols fibers. ll desired the fibers may be those graft-copolymerized with eopolymerizahlc vinyl monomers. The fabric may be knit, woven or non-woven, or be any otherwise constructed fibric.

In carrying out the method of this invention, a fabric is first impregnated with an aqueous liquid containing an aldehyde or a substance which is capable of liberating an aldehyde under the treating condition, such as paraform, methylol hydantoin, glyoxal, glutal aldehyde, acetal, hexamethylene, tetramine, etc. However formaldehyde is most preferred in this invention.

An aldehyde (e.g. formaldehyde, glyoxal) or a substance capable of liberating an aldehyde is applied to a fabric in the form of aqueous solution or liquid by any suitable manner such as by spraying the liquid on the fabric or immersing the fabric in the liquid followed by squeezing. In any event, however, the fabric to be subjected to the subsequent gaseous acid treatment should contain about i 25 percent, preferably 4 15 percent by weight of an aldehyde (as available component) or an aldehyde-liberating compound (as available aldehyde) based on the weight of the fabric. Generally, an aqueous liquid containing from 1 to 50 percent (usually 5 20 percent) by weight of an aldehyde (as available component) or containing an aldehyde-liberating substance in such an amount that it would liberate an aldehyde in a concentration of from 1 to 50 percent (usually 5 20 percent) by weight in the liquid is employed. The liquid is applied to the fabric by spraying or dipping so that the fabric has a wet pick-up of 50 100 percent (usually 60 percent) by weight. If necessary, the fabric is squeezed to attain the pick-up recited above.

It is preferable that the solution of an aldehyde or an aldehyde-liberating substance contains a formaldehyde (or aldehyde) catcher. The term catcher as an is intended to mean a substance which is capable of holding or retaining formaldehyde (or an aldehyde) during drying and subsequent acid treating stage to prevent the dissipation of the aldehyde. Examples of such aldehyde catcher are polyacrylates such as polyethylacrylate, polybutylacrylate, polyethyl-butylacrylate, polyhydroxyethylacrylate, etc. and cellulose ethers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, etc. Usually those polyacrylates and cellulose ethers are commercially available as aqueous solution or emulsion of solid content of 20 to 40 percent. In carrying out the invention, such an emulsion or solution is added to the liquid containing the aldehyde or an aldehyde-liberating substance so as to be in a concentration of from 1 to 10 percent (as such emulsion or solution) by weight.

The solution may also contain a small amount of suitable blueing agent, brightening agent, softener (lubricant), etc. Particularly a softener or lubricant will affect the wash and wear properties and strength of the fabric resulting from the treatment according to this invention. For the purpose of this invention, preferable softeners or lubricants are polyolefine type softeners such as polyethylene, polypropylene, etc. and silicone type softeners such as those commercially available under the trade mark Noran Silicone Softener. These softeners will impart to the fabric desirable soft hand, good wash and wear properties and desired balance of dry and wet resilience and strength of the fabric. It is most preferable to employ a polyolefine type softener and a silicone type softener together. The amount of the softener or lubricant is not critical but generally a satisfactory result is obtained when it is added to the aldehyde (or formaldehyde-liberating substance) solution so as to be a concentration of from 1 percent to 6 percent by weight.

After impregnated with the liquid containing an aldehyde or an aldehyde-liberating substance, the fabric is contacted with gaseous hydrochloric acid, sulfur trioxide or sulfur dioxide and subjected to an acetalizing or cross-linking reaction between the cellulose and aldehyde. As mentioned before the moisture (calculated as water) content of the fabric during the contact with gaseous HCl, 80;, or S0 and the reaction should be so controlled as to be below 20 percent by weight based on the fabric weight. Therefore, it is usually necessary that the fabric is dried before the acid treatment so that the fabric, when entering in the gaseous acid treating stage, has a moisture content within the required range, namely 3 20 percent (preferably 6 15 percent). The fabric may be dried in any suitable manner at a temperature from room temperature up to about 120 C.

The fabric with the above mentioned moisture content is then contacted with the gaseous acid (catalyst for the reaction between the aldehyde and cellulose). This is accomplished by contacting or exposing the fabric to an atmosphere containing the gaseous acidic substance. The atmosphere to be contacted with the fabric should contain 1 100 percent by volume, preferably 5 40 percent by volume, of gaseous hydrogen chloride, sulfur trioxide or sulfur dioxide and be maintained at a temperature below 50 C., preferably between about C. and 50 C. By this contact, the acidic substance or catalyst is applied to the fabric because the gas is penetrated or dispersed into and absorbed by the fabric.

ln supplying such gaseous acidic substance in contact with the fabric, any suitable means may be employed. For example, an open vessel containing hydrochloric acid in a desired concentration is placed at the bottom of a closed chamber and the said container is heated so that gaseous hydrogen chloride vaporized from the container will fill the interior of the chamber through which the fabric may be passed. Alternatively, hydrogen chloride gas or sulfur dioxide or trioxide gas as separately prepared may be continuously introduced into a closed chamber through which the fabric may be passed. If desired, it is possible to directly blowing an acidic gas against a travelling fabric. Usually a fabric is continuously travelled in one direction and a gaseous acidic substance is applied or contacted to the fabric at a predetermined region of the passage. Alternatively, the fabric is placed in a closed chamber (containing the gaseous acidic substance) as rolled up on a rotatable roller. A second rotatable roller is arranged within the same chamber and spaced from the first roller. Within the chamber the roller is driven so that the fabric roll on the first roller is continuously unwound therefrom and rewound up on the second roller. When the fabric is completely rolled or wound up on the second roller, the driving direction is reversed so that the fabric is unwound from the second roller and rewound up around the first roller. During the movement from the first roller to the second roller or vice versa the fabric is contacted with or exposed to the acidic gas. This unwinding and rewinding is repeated until the fabric has contacted the treating gas for a desired period of time. In still another embodiment, a fabric is contacted with a continuously travelling porous belt impregnated with hydrochloric acid of a desired concentration so that during the contact with the belt the fabric is applied with hydrogen chloride gas developed from the hydrochloric acid within the belt. In this case, care should be taken that the fabric would not directly contact with the hydrochloric acid liquid contained in the belt.

In any case the contact of the fabric with gaseous hydrogen chloride, sulfur dioxide or sulfur trioxide should be effected at a temperature below 50 C., preferably between 20 C. and 50 C. The time during which the said contact is carried out varies very widely depending upon and is corelated with the temperature, particular acid employed, the concentration of acid in the atmosphere to be contacted with the fabric. Hydrogen chloride or sulfur trioxide is more reactive and therefore requires shorter treating time and/or lower temperature than sulfur dioxide. When the acid concentration in the atmosphere to be contacted with the fabric is higher, a shorter time and/or lower temperature may be employed. In any case, however, the contact should be such that the fabric absorbs the acidic catalyst in an amount sufficient to cause the desired acetalization or cross-linking reaction. As mentioned before the time for contacting the fabric with the gaseous acidic catalyst varies over a wide range, namely only one or few seconds to even 90 minutes or more, depending largely upon the concentration of the gas and the temperature at which the contact is carried out.

Upon contact of the fabric with the gaseous acid catalyst the reaction between the aldehyde and cellulose is commenced. The desired reaction may be completed while contacting the fabric with the gas. Alternatively, it is possible to contact the fabric with the gas until a desired amount of the acidic catalyst is applied to or absorbed by the fabric at a temperature below 50 C. and then leave the fabric to stand in an acid-free atmosphere at a temperature below 50 C. until the reaction is proceeded to a desired extent, if the reaction has not been proceeded to the desired extent during the contact of the fabric with the gas.

By way of examples, when a cotton fabric is immersed in an aqueous solution containing 35 percent by weight of formaldehyde (38 percent), squeezed to a wet pick-up of 70 percent and then dried to a moisture content of 10 percent by weight, a satisfactory result is obtained if the dried fabric is passed through a closed chamber containing the following HCl gas at the following temperature for the following period of time during which the desired reaction is completed:

Temperature HCI gas conc. Time C.) (vol.%) (minute) 20 10 20 40 l 30 10 1% 3O 40 V4 40 10 5: 4O 40 1/12 40 5 2 In still another example the same dried fabric was passed through a chamber wherein a gas containing 5 percent by volume of hydrogen chloride gas was positively blown against the fabric at 30 C. for 10 minutes. Immediately thereafter the fabric was left to stand in an atmospheric condition (acidfree) at 30 C. for seconds to obtain the result substantially same as that obtained in the cases mentioned in the above table.

Thus, the time for contacting the fabric with the gaseous acidic catalyst and whether or not the fabric should be left standing after the said contact vary widely under the particular circumstance involved but should be easily determined by those skilled in the art.

The atmosphere to be contacted with the fabric may contain, in addition to the gaseous acid, other gaseous components such as air, nitrogen gas and moisture (water) which do not affect the reaction involved. The moisture condition in the treating atmosphere may be neglected in connection with the moisture content of the fabric mentioned before.

Throughout the handling and treatment of the fabric, inclusive squeezing, drying, acid treatment and the subsequent reaction (if any), the fabric should be kept at its open width because the creases or wrinkles formed on the fabric during the process are difficult to be removed or recovered and lead to critical loss in the marketability of the product.

Immediately after the acid treatment or the subsequent reaction (if any), the fabric is washed to remove any acid and free material remaining on the fabric. The washed fabric is then dried.

A cellulosic fabric may be subjected to the method of this invention without any pretreatment of the fabric. However, it is preferable to employ a preliminarily mercerized fabric in this invention, because a mercerized fabric is imparted with desirable wash and wear performance more easily according to the method of this invention. The mercerization is well known in the art and no detailed explanation thereabout would be necessary.

It has further been found that when the fabric is subjected to alkylation or substituted-alkylation before carrying out the method of this invention, more improved characteristics of wash and wear properties and more improved balance between the wet and dry resilience and strength of the fabric are obtained according to this invention. The alkylation or substituted-alkylation may be carried out in a conventional manner by treating the fabric with an alkylation (or substituted-alkylation) agent in the presence of an alkaline condition. Thus, for example, dialkyl sulfate, e.g. dimethyl sulfate, diethyl sulfate; alkyl or substituted alkyl halide, e.g. butyl chloride, ethyl chloride, butyl bromide, ethyl bromide; ethylene chlorohydrine, ethylenebromohydrine, chloroacetic acid, bromoacetic acid, etc. may be used as alkylation or substituted-alkylation agents. When hydroxyalkylation is desired ethylene oxide, propylene oxide or the like may be employed. In carrying out the alkylation or substituted-alkylation, a fabric is impregnated with an aqueous solution (5 percent by weight or more in concentration) of the alkylation (or substituted alkylation) agent and squeezed. The fabric is further impregnated with a strong percent by weight or more) aqueous alkali solution, for example, of sodium hydroxide or potassium hydroxide, and then squeezed. If the alkylation or substituted-alkylation agent is insoluble in water it may be applied to the fabric in the form of emulsion. If the alkylation or substituted alkylation agent is reactive with water it may be applied to the fabric in the form of a solution in an organic solvent for example, alcohol or benzene. The alkylation or substituted-alkylation may be carried out on a conventional mercerizing machine. It is preferable that the alkylation or substituted-alkylation degree is such that 2 5 mols of alkyl or substituted alkyl groups are introduced per 100 glucose units constituting the fabric fibers.

The invention will be further illustrated by reference to the following Examples. In these Examples various properties of fabrics have been determined by the following methods:

Tensile strength ASTM D39-49 Grab method, in

respect of warps.

By the method described in American Dyestuff Reporter, Vol. 45, P. 472 (1956), and indicates by the sum of values for fillings and warps.

ASTM-D-l 295-53T; indicated by the sum of values for fillings Wet resilience Dry resilience and warps. Wash and wear Determined by comparing with properties Monsanto Plastic Model. Tear strength ASTM-D-l424-56T (Elmendorf method) Laundry By AATCC Tentative Test Method 88-1960-4a.

EXAMPLE 1 A sample of mercerized cotton poplin was immersed in a bath of the following recipe, squeezed to a wet pick up of 65 percent and dried at 100 C. to reduce the moisture content to 8 percent by weight.

Formaldehyde (37%) Polyethylene emulsion 2 Noran Silicone Softener 2 Water to 100 Wet resilience Dry resilience Tensile strength Wash and wear property 283 degrees 261 degrees The resulting fabric had a neat appearance and a very soft hand, and there was no increase in the weight. The wet and dry resilience or the wash and wear properties of the fabric were improved remarkably by the above treatment, while accompanying no noticeable reduction in the tensile strength and tearing strength. There is no appreciable reduction in the wet and dry resilience of the fabric even after 10 cycles of laundering.

EXAMPLE 2 The procedure of Example 1 was repeated except that the fabric, after the immersion in the formaldehyde solution and the subsequent drying, was passed through a chamber maintained at 20 C. for 15 minutes. Within the chamber and at the bottom thereof an open container had been placed containing 36 percent hydrochloric acid so that the chamber contains about 6 percent by volume of hydrogen chloride gas during the treatment of the fabric. Immediately after this hydrochloric treatment, the fabric was washed sufficiently with water and dried. The treated fabric was tested and the results are given in the following table. In this table are also given the corresponding data in respect of a conventional resin finished fabric and also in respect of a conventional resin finished fabric and also in respect of a conventional formaldehydetreated fabric, for comparison.

Wash Resilience Tensile and wear properties (degrees) strength (kg.) After 1 After 10 Sample dry wet cycle of cycles of laundering laundering Untreated 28.8

A 252 278 15.6 4.8 4.7 B 230-250 210-230 17.0-18.5 3.3 3.0 C 200-220 230-250 17.5-19.0 2.8

A The fabric treated according to Example 2.

B The resin finished fabric. The fabric was immersed in an aqueous bath containing l0% of triazone type resin precondensate (50% 2% of zinc nitrate (40%) and 2% of polyethylene emulsion (20%). The fabric was squeezed to a wet pick-up of 65% and dried at C. for 2 minutes. The fabric was then subjected to baking at C. for 3 minutes.

C The conventional formaldehyde-treated fabric. The fabric was immersed in an aqueous bath containing 10% of formaldehyde (37%), 2% of oxalic acid (crystal) for 2% of polyethylene emulsion (20%). The fabric was squeezed to a wet pick-up of 65% and dried at l25 C. for 3 minutes. Then the fabric was dried at 160 C. for

3 minutes.

EXAMPLE 3 A poplin of viscose rayon staple fibers graft copolymerized with ethyl acrylate (the rate of graft; 35 percent by weight) was immersed in an aqueous solution containing 30 percent of formaldehyde (37 percent) and 3 percent of ehtyl cellulose (solid content 20 percent). The fabric was squeezed to a wet pick of 65 percent and dried at 1 10 C. to reduce the moisture content to 10 percent. The dried fabric was then passed through a closed chaMber (25 C.) which interior air had been substantially replaced by hydrogen chloride gas so that the chamber contains about 6 percent (by volume) of hydrogen chloride gas. After passing through the chamber for 10 minutes, the fabric was washed with water and dried. The fabric was tested and the results were as follows:

Resilience Tensile Wash & wear (degrees) strength properties Dry Wet Before treatment (without grafting 23.2 kg.

After treatment 262 282 18.1 kg. 4.6

EXAMPLE 4 A mercerized cotton poplin was immersed in an aqueous solution containing 13 percent of hexamethylene tetramine, 2 percent of Noran Silicone Softener (a silicone type softener), 4 percent of polyethylene emulsion (solid content 20 percent) and 0.01 percent of a penetrating agent. The fabric was then squeezed to a wet pick up of 70 percent and dried at 1 10 C. to reduce the moisture content to l0 percent. Then the fabric was contacted for 20 minutes with a polystyrene sponge sheet impregnated with 36 percent hydrochloric acid and heated at 50 C. During this contact, the fabric was exposed to a gas containing 1 percent (by volume) of hydrogen chloride gas. Immediately after this hydrochloric treatment the fabric was washed and dried, and subjected to testing. The results were as follows:

Treated Untreated Tensile strength 25.3 kg. 30 kg. Tear strength 1459 g. 1000 g. Resilience:

Dry 2 l 5 degrees Wet 221 degrees Wash & wear performance 3.5

EXAMPLE 5 A mercerized cotton poplin was immersed into an aqueous liquid containing 35 percent of formaldehyde (37 percent), 2 percent of polyethylene emulsion (solid content 20 percent) and 2 percent of polyethyl-butylacrylate (solid 30 percent). Then the fabric was squeezed to a wet pick-up of 65 percent and dried to a moisture content of percent. The fabric wound up on a roller and placed within an autoclave in which was arranged a second winding roller spaced from the first roller. The air in the autoclave was replaced by sulfur dioxide so that the interior volume of the autoclave contains about 10 percent by volume of sulfur dioxide at 50 C. The rolled fabric was unwound from the first roller and rewound on the second roller and then vice versa. This unwinding and rewinding was repeated until the fabric has contacted the S0 gas atmosphere for 20 minutes. Then the fabric was washed with water and dried. The fabric was tested and the results were as follows:

Tensile strength 13.1 kg. Tear strength 278 g. Resilience:

Dry 263 degrees Wet 275 degrees Wash and wear properties 4.]

EXAMPLE 6 A mercerized cotton poplin was immersed in an aqueous liquid containing 35 percent of formaldehyde (37 percent), 2 percent of polyethylene emulsion (solid 20 percent) and 2 percent of polyethyl-butyl acrylate (solid 30 percent). Then the fabric was squeezed to a wet pick-up of 65 percent and dried at a temperature of 100 C. to a moisture content of 10 percent. The fabric was contacted with a continuously travelling polystyrene sponge containing 36 percent hydrochloric acid for minutes at 40 C. so that the fabric was exposed to an atmosphere containing about 3 percent by volume of gaseous hydrogen chloride. After washing and drying the fabric was tested. This fabric showed 4.5 in the wash and wear performance.

EXAMPLE 7 A mercerized cotton poplin was immersed in an aqueous solution containing 10 percent by weight of monochloroacetic acid, squeezed to a wet pick-up of 65 percent, then immersed in 30 percent aqueous solution of sodium hydroxide and squeezed to a wet pick-up of 70 percent, and the reaction was allowed to proceed for 2 minutes while holding the edges of the fabric to keep the same at the open width. Then the fabric was washed with water, neutralized, again washed and dried.

The carboxymethylated poplin was immersed in an aqueous liquid containing 30 percent of formaldehyde (37 percent) and 4 percent of polyethylene emulsion (solid percent). Then the fabric was squeezed to a wet pick-up of 65 percent and dried to a moisture content of 10 percent. The fabric was then passed through a closed chamber filled with an atmosphere containing 80 percent (by volume) of gaseous hydrogen chloride, at 35 C. for 5 seconds. For comparison, the same procedure was repeated with the same mercerized cotton poplin but not carboxymethylated. The test results for these fabrics after washing and drying were as follows:

Resilience Tensile Wash & wear dry wet strength properties Untreated 28.0 kg. Carboxymethylation-lformaldehyde treat 245 280 14.5 kg. 5.0 Formaldehyde treatment only 240 270 13.5 kg. 4.7

EXAMPLE 8 A mercerized cotton poplin was immersed in an formaldehyde solution of Example 6, squeezed to a wet pickup of 65 percent and dried at 100 C. to a moisture content of [0 percent. Then the fabric was passed through a closed chamber of an atmosphere containing 10 percent (by volume) of hydrogen chloride gas at 40 C. for 30 seconds. For comparison the same procedure was repeated with using the same mercerized cotton poplin but carboxymethylated as in Example 7. The test results for these fabrics are as follows:

Resilience Tensile Wash & wear dry wet strength properties Carboxymethylation formalde' 270 290 14.1 kg. 4.8 hyde treat Formaldehyde treatment only 240 270 13.7 kg. 4.5 Untreated 28.0 kg.

EXAMPLE 9 The procedure of Example 7 was repeated except that 15 percent aqueous solution of ethylenechlorohydrine was employed instead of monochloroacetic acid solution. The tests of this fabric disclosed that it is excellent in both wash and wear property and balance between resilience and strength.

EXAMPLE 10 A satin cloth composed of highly polymerized cellulosic fibers (so-called Polynosic" and sold by Toyo Spinning Co., Ltd. under the trade mark Tufcel") was immersed in an aqueous liquid containing 20 percent of formaldehyde (35 percent), 4 percent of polyethylene emulsion (solid 20 percent) and 2 percent of polyethyl-butylacrylate (solid 30 percent). Then the fabric was squeezed to a wet pick-up of 65 percent and dried at 100 C. to a moisture content of 12 percent. The fabric was passed through a closed chamber of an atmosphere containing 5 percent (by volume) of hydrogen chloride gas at 50 C. for 30 seconds. Then the fabric was washed and dried, and tested. The test results were as follows:

Resilience Tensile Wash & wear dry wet strength properties Example 10 267 286 11 kg. S Untreated 20 kg.

EXAMPLE 1 l A cotton poplin was immersed in an aqueous bath containing 35 percent of formaldehyde (38 percent), 4 percent of polyethylene emulsion (solid 20 percent) and 2 percent of Noran silicone softener. The fabric was squeezed to a wet pick-up of 70 percent and dried to 8 percent. The dried fabric was passed through a closed chamber maintained at 30 C. for seconds while feeding hydrogen chloride gas to the chamber so that the latter contains about 12 percent (by volume) of hydrogen chloride gas during the treatment. immediately often this treatment the fabric was washed and dried. The test results were as follows:

Tensile strength 15.0 kg. Tear strength 700 g. Dry resilience 270 degrees Wet resilience 290 degrees Wash and wear properties 4.7

EXAMPLE 1 2 seconds through a closed chamber maintained at C. and containing 14 percent by volume of hydrogen chloride gas. After the treatment, the fabric was washed and dried. The properties of this fabric were as follows:

Tensile strength 15.5 kg. Tear strength 700 g.

Dry resilience 270 degrees Wet resilience 300 degrees Wash and wear properties 5.0

EXAMPLE 13 A cotton poplin was immersed in the aqueous solution of Example 11, squeezed to a wet pick-up of 75 percent and dried to a moisture content of 7 percent. Then the fabric was passed for 20 seconds through a closed chamber maintained at 30 C. and containing 7 percent by volume of hydrogen chloride gas. After the passage through the chamber, the fabric was left standing for 60 seconds in an atmospheric condition at 30 C. Then the fabric was washed and dried. The properties of the fabric were as follows:

Tensile strength 15.0 kg. Tear strength 700 g.

Dry resilience 270 degrees Wet resilience 270 degrees EXAMPLE 14 Tensile strength l6.0 kg. Tear strength 750 g. Dry resilience 240 Wet resilience 285 Wash and wear properties 4.5

It will be clear from the foregoing description and various Examples that the present invention provides a novel and simple method for treating a cellulosic fiber-containing fabric to improve its wash and wear performance or wet and dry resilience without a noticeable sacrifice of its mechanical strength. One feature of this invention is in the fact that a cross-linking agent (e.g.) formaldehyde and an acidic catalyst (e.g. hydrochloric acid) are applied separately in contrast to conventional method. Another feature of the invention is in the fact that the acidic catalyst is applied in the form of gas to a fabric and in the presence of a controlled small amount of water within the fabric.

What is claimed is:

1. A process of treating a cellulosic fiber-containing fabric to improve its wet and dry resilience, which comprises impregnating the fabric with an aqueous liquid containing as the sole active fiber treating agent a compound selected from the group consisting of formaldehyde and formaldehyde liberating compounds in an amount of l-25 percent by weight based on the fabric weight, drying the fabric to a moisture content of 3-20 percent by weight and then contacting the dried fabric with a gaseous acidic substance selected from the group consisting of sulfur trioxide and sulfur dioxide, at a temperature below 50 C.

2. A process as claimed in claim 1 wherein the fabric is dried to a moisture content between 6 percent and 15 percent by weight.

3. A process as claimed in claim 1 wherein the formaldehyde or formaldehyde liberating substance is impregnated in the fabric in an amount of 4-l5 percent by weight based on the fabric weight.

4. A process as claimed in claim 1 wherein the fabric to be contacted with the gaseous acidic substance also contains a softener selected from polyolefine type softeners and silicone type softeners.

5. A process as claimed in claim 1 wherein the contact of the fabric with the gaseous acidic substance is carried out by exposing the fabric to an atmosphere containing at least 1 percent by volume of the gaseous acidic substance.

6. A process as claimed in claim 1 wherein the fabric is mercerized prior to said impregnation.

7. A process as claimed in claim 1 wherein the fabric is subjected to an alkylation or substituted-alkylation prior to said impregnation.

8. A process as claimed in claim 1 wherein the aldehyde is formaldehyde. 

2. A process as claimed in claim 1 wherein the fabric is dried to a moisture content between 6 percent and 15 percent by weight.
 3. A process as claimed in claim 1 wherein the formaldehyde or formaldehyde liberating substance is impregnated in the fabric in an amount of 4-15 percent by weight based on the fabric weight.
 4. A process as claimed in claim 1 wherein the fabric to be contacted with the gaseous acidic substance also contains a softener selected from polyolefine type softeners and silicone type softeners.
 5. A process as claimed in claim 1 wherein the contact of the fabric with the gaseous acidic substance is carried out by exposing the fabric to an atmosphere containing at least 1 percent by volume of the gaseous acidic substance.
 6. A process as claimed in claim 1 wherein the fabric is mercerized prior to said impregnation.
 7. A process as claimed in claim 1 wherein the fabric is subjected to an alkylation or substituted-alkylation prior to said impregnation.
 8. A process as claimed in claim 1 wherein the aldehyde is formaldehyde. 